I've been getting complaints that email sent from the server is going to Yahoo's bulk/junk folder. It turns out that it is being sent from server.mydomain.com but the RDNS points to ns1.mydomain.com.

So, my guess is that I shouldn't have assigned the ns1 ip to be the same as server.mydomain.com.

What should I do? I thought about changing the hostname, but in the docs it says:
"This means that your hostname should never be a domain name and especially not the name of your domain!!". So I'm guessing that changing it to ns1 is a bad idea.

So, then I'm guessing I need to change ns1 to a different IP. My concern is that I have 20+ domains on this server and if I change the IP, I'm not sure if that requires a change for each of the domain registrars?